In the third chapter rhetoric is separated into five parts: invention, arrangement, style, mem-ory, delivery. I am now not at all surprised that Quintilian is so bereft of dialectic in this division, for he was unable to recognize that here he h is confused dialectic itself with rhetoric, since in-vention, arrangement, and memory belong to di-alectic and only style and delivery to rhetoric. Indeed, Quintilian's reason for dividing rhetoric into these five parts derived from the same single source of error as did the causes of the previous confusion. The orator, says Quintilian, cannot be perfected without virtue, without grammar, with-out mathematics, and without philosophy. There-fore, one must define the nature of the orator from all these subjects. The grammarian, the same man says, cannot be complete without mu-sic, astrology, philosophy, rhetoric, and history. Consequently there are two parts of grammar, methodology and literary interpretation. As a re-sult Quintilian now finally reasons that rhetoric cannot exist unless the subject matter is first of all discovered, next arranged, then embellished ' and finally committed to memory and delivered. Thus these are the five parts of rhetoric.
Grammar may be necessary to use in rhetoric and virtue may be an important part of a good orator, but rhetoric is not about grammar or virtue. Rhetoric is about style and delivery.